I'm not sure if this is intentional and I did attempt to look through the previous issues to see if this had already been reported.

It seems that the connectors don't respect if a belt is split and keep it that way. They seem to alternate between each item using the full belt.

split belt going in:
https://imgur.com/3aHxKsr

alternating belt coming out:
https://imgur.com/Bhrybdb

From the mod description:

Items are mixed randomly in the left and right lanes of output belts. This makes Beltlayer only usable with belts carrying the same item in both lanes, or "sushi belt" designs that don't have any item placement requirements. This is a limitation of Factorio's loader entities.

my apologies, that is sad but understandable